Audio signal generator

Abstract

Audio frequency signal generator to generate signals in a selected band of audio frequencies to generate a noise having an amplitude pattern which simulates the noise generated by a selected occurrence which can be utilized for setting the actuation range of an audio actuated alarm device which is capable of discriminating the noise generated by such an occurrence where the generated frequency of the sound and amplitude of the sound waves can be varied selectively to simulate the pattern of the sound waves emanating from the selected occurrence.

The invention claimed is: 
     
       1. An audio frequency generator to generate signals in a selected band of frequencies including: (a) signal generator means to generate first cyclical signals of selected frequency having a first output to supply said first cyclical signals;   (b) electrical power source means;   (c) first switch means having first switch actuation means input to receive said first signals, power input means to receive electrical power from said power source means and a power output wherein said first switch means is operated between first state and second state, in response to signals received at said first switch actuation input means, to supply electrical power at said power output when said first switch is in said first state whereby power is cycled at a rate determined by the frequency of said first signal wherein said first switch means includes:   (i) first transistor means to receive said first cyclical signals at the actuating input thereof and having said power source connected to an input thereof and an output connected to ground means so said first transistor is switched between first state wherein said first switch is in conductive status and said second state where said first switch is in nonconductive status by said first cyclical signals to provide a second cyclical signal at said input proportional to said first cyclical signal;   (ii) second and third transistor means in series with each other where the actuation means of said second transistor means and said third transistor means are connected to said input to said first transistor means to be actuated by said second cyclical signal as said first transistor switches between conductive and nonconductive states in response to said first cyclical signal wherein said second transistor means is actuated to conductive state by a relatively positive portion of each of said second cyclical signal and third transistor means is actuated to conductive state by the relatively negative portion of said second cyclical signal and where the collector of said second transistor is connected to said power supply means, the emitter of said second transistor is connected to the collector of said third transistor and the emitter of said third transistor is connected to ground means and where said speaker means is connected to said collector of said second transistor whereby power is supplied to said speaker means when said second transistor means is conductive and said third transistor means is nonconductive.   (d) speaker means adapted to be actuated by said power output whereby said speaker provides audio signals of selected amplitude at frequencies generally corresponding to the frequency of said first signals;   (e) where said power source includes a source of electrical current and capacitor means to be charged when said first switch means is in said first state and discharged through said speaker means when said first switch is in said second state whereby the amplitude of said audio signals is proportional to the voltage imposed on said capacitor so the amplitude of said audio signal decreases as the voltage of said capacitor diminishes;   (f) second switch operable between first state in response to first voltage at said capacitor means and second state in response to second voltage at said capacitor means where said second voltage is higher than said first voltage and wherein said second switch means prevents transmission of signals generated by operation of said first switch to said speaker means when said second switch is in said first state and allows transmission of signals generated by said first cyclical signals to said speaker means when said second switch means is in said second state whereby audio signals of variable frequency are provided from said speaker means at amplitudes depending on the voltage at said capacitor means for a period of time equal to the time required for the voltage at said capacitor to decrease from said second voltage to said first voltage.   
     
     
       2. The invention of claim 1 including: (a) inverter means connected to said first output of invert said first cyclical signal to provide an inverted first cyclical signal;   (b) third switch means having a third switch signal input to receive said inverter first cyclical signal and third switch power input means to recive electrical power from said power source means and a power output connected to ground where said input means is operated between first and second states in response to signals received at said third switch signal input to supply electrical power at said power input at a rate generally equal to the frequency of said first inverted signal so said first switch is in said first state when said second switch is in said second state wherein said speaker means are also actuated by said power output at the frequency of said inverted first signals to provide audio signals of selected amplitude at frequencies generally corresponding to the frequency of said inverted first signals.   
     
     
       3. The invention of claim 1 wherein said second switch means includes: (i) fourth transistor means to receive said inverted first cyclical signals at the actuating input thereof and having said power source connected to an input thereof and an output connected to ground means so that said first transistor is switched between conductive states, and noncondictive states by said inverted first cyclical signals to provide third cyclical signal at said input proportional to said inverted first cyclical signal;   (ii) fifth and sixth transistor means in series where the actuating means of said fifth transistor means and said sixth transistor means are connected to said input to said second transistor means to be actuated by said third cyclical signal between conductive and nonconductive states in response to said third cyclical signal wherein said fourth transistor means is actuated to conductive state by a relatively positive portion of each of said third cyclical signal and said sixth transistor means is actuated to conductive state by the relatively negative portion of said third cyclical signal and where the collector of said fourth transistor is connected to said power supply means, the emitter of said fourth transistor is connected to the collector of said sixth transistor and the emitter of said sixth transistor is connected to electrical current sink means and where said speaker means is connected to said collector of said fourth transistor whereby power is supplied to said speaker means when said fourth transistor means is conductive and said sixth transistor means is nonconductive.